Topological designs of mechanical-electromagnetic integrated laminate metastructure for broadband microwave absorption based on bi-directional evolutionary optimization

Microwave absorption plays an important role on many aspects such as stealth technologies and electromagnetic compatibility. In this work, topological optimization is applied for the proposed laminate metastructure (LM) to achieve broadband and wide incident-angle microwave absorption. A new and efficient version of genetic algorithms (GA), namely the large mutation genetic algorithms (LMGA) is introduced in the bi-directional evolutionary optimization (BEO) methodology which is distinguishing from the traditional bi-directional evolutionary structural optimization (BESO). Topological optimization for patterned resistive films and size optimization for spacer thickness are integrated in the program. The optimized two-dimensional patterns of the metasurface are given. The thickness optimization range is limited below 4 mm to reduce the total thickness of LM. The optimized and fabricated specimen achieves −10dB absorption bandwidth in 2.0–22.9 GHz with total thickness of 16.05 mm, small areal density of 4.19 kg/m² and equivalent flexural strength of 23.12 MPa. A three-stage nonlinear model on the bending and buckling of LM is given, and the experimental and theoretical deflection-load curves match well. The proposed LM achieves multifunctional features of broadband microwave absorption and effective mechanical resistance.